RFR: 8359437: Make users and test suite not able to set LockingMode flag

[Coleen Phillimore]

On Wed, 18 Jun 2025 07:52:02 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This PR contains changes for the 1st phase of the `LockingMode` flag obsoletion. 
>> 
>> The work is done by @fbredber, I have taken it over and am finishing it while he's on vacation. 
>> 
>> In the 1st phase one keeps the `LockingMode` variable in all places, but makes it non-settable from the command line. All the C1 and C2 code related to legacy locking will still be in place (but as dead code) and removed later (phase 2).
>> 
>> Lightweight locking is the default locking from now on.
>> 
>> Tested in tiers 1 - 7.
>
> test/hotspot/jtreg/runtime/vthread/JNIMonitor/JNIMonitor.java line 1:
> 
>> 1: /*
> 
> This seems to remove significant test coverage. can we not adapt the tests to not rely on logging warnings that will no longer be present?

The premise of this test is now invalid.  We could write a fresh new test if we'd like to see what happens with UseHeavyMonitors, and/or retrieve this from git history.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25847#discussion_r2155250065